Wireless communications systems are becoming an increasingly integral aspect of modern communications. In fact, recent trends show that an increasing number of users are replacing all wire-line methods of communications with their wireless counterparts such as, for example, cellular telephones in place of traditional wire-line telephones. Since such cellular telephones are essentially radios, it is well known that signal quality between a cellular base station and a handset degrades under certain circumstances. The most significant source of degradation occurs when a user moves from an outside location to an indoor location where the radio signals are required to pass through or around various obstructions. Since many users place the majority of cellular calls from within buildings or other structures, achieving high quality consistent indoor coverage is becoming more essential.
Several methods for achieving indoor cellular network coverage are known. For example, one method of achieving such coverage, known as a distributed antenna system (DAS), is illustratively shown in FIG. 1. A DAS uses a base station and a repeater or a power amplifier that is typically located within a building to retransmit within the building a signal received at an external antenna. Referring to the illustrative DAS of FIG. 1, when a signal 103 is transmitted from an antenna in a cellular communications network, such as antenna 101 (e.g., an antenna in a cellular communications network), antenna 113, which is external to building 111, receives signal 103. Signal 103 is then passed along connection 104 which is, illustratively, a coaxial cable, to component 105 which is, in this example, a radio repeater. Repeater 105 forwards the signal to amplifiers 106a, 107a, 108a and 109a. These amplifiers amplify the signal which is then transmitted over in-building antennas 106, 107, 108 and 109. Thus, the result is that cellular telephone 102 receives the signal transmitted from antenna 113 via antenna 109. By passing the signal along a wired connection from antenna to repeater 105 and rebroadcasting the signal over antennas 106-109, the problems associated with poor signal quality in buildings are alleviated.
While DAS systems are advantageous in many aspects, they are limited in certain regards. For example, in order to install a DAS, cabling (such as coaxial cabling) must be installed throughout the building at each location where an in-building antenna is desired. Thus, installation expense is relatively high. Additionally, such systems are not flexibly expandable and there is typically no mechanism for reprovisioning or reallocating the bandwidth available to different locations within the building.
Another method for achieving indoor cellular network coverage relies on the use of small in-building base transceiver stations (BTSs), which are smaller versions of well-known base stations such as are used in a traditional cellular network, to provide essentially an entire in-building cellular network. The result of using such small BTSs is a network of so-called pico-cells (cells with a short range) that operate similarly to a low-powered traditional cellular network in provisioning bandwidth and managing data and voice calls within one or more individual buildings. However, since such a system is essentially a miniaturized cellular network, management of a multitude of such BTSs within a building would be problematic as it would require network components (such as a Radio Network Controller (RNC) and/or a Mobile Switching Center (MSC) in a CDMA network) to provision bandwidth and manage calls across the large number of pico-cells. Hence, a mini-BTS system is relatively cost-prohibitive and complex to install and maintain.
As cellular usage increases there is a need to provide increased and cost effective capacity and coverage outdoors in dense urban areas, outdoor malls, or in business or academic campuses. Many of the same techniques that are used indoors can also be used in these environments. Typically a base station remotely serves a given outdoor location using DAS systems in an architecture known as “hoteling”. However, these architectures require the use of proprietary RF or fiber links to connect the base stations and the remote antennas.